Abstract
A new organic reagent, 5,5-dimethyl-2-(2-hydroxy-3,5-disulfophenylhydrazo)сyclo-hexane-1,3-dione (H2L), was synthesized by azo coupling of diazonium salts of 2-hydroxy-3,5-disulfoaniline with dimedone. The dissociation constants of H2L were determined by potentiometric titration, being pK 1 = 5.90 ± 0.03 and pK 2 = 9.67 ± 0.04. The interaction in systems of H2L and cationic surface-active substances (CSAS), cetylpyridinium chloride (CPCl), cetylpyridinium bromide (CPBr), or cetyltrimethylammonium bromide (CTABr) was studied in the presence and absence of Cu(II). It was found that the detection limit of Cu(II) using H2L–CSAS pairs decreases in accord with the stability of associates H2L(CPCl)2 > H2L(CPBr)2 > H2L(CTABr)2 and their copper(II) complexes Cu[(HL)(CPCl)2]2 > Cu[(HL)(CPBr)2]2 > Cu[(HL)(CTABr)2]2. The effects of foreign ions and masking substances on the complexation were studied and showed that the reaction of Cu(II) with H2L in the presence of CSAS is more selective. Based on these observations, a procedure for the spectrophotometric determination of copper(II) in soils polluted by oil, seawater, igneous rock, and nickel-based alloys was developed.
This work has been partially supported by the Foundation for Science and Technology (FCT), Portugal, and its PPCDT (FEDER funded), and “Science 2007” programs. K. T. Mahmudov and M. N. Kopylovich express gratitude to the FCT for their post-doctoral fellowship and working contract. The authors also acknowledge the Portuguese NMR Network (IST-UTL Center) for providing access to the NMR facility.
Notes
*No interference.